Migrating to v4

Bootstrap 4 is a major rewrite of the entire project. The most notable changes are summarized below, followed by more specific changes to relevant components.

Stable changes

Moving from Beta 3 to our stable v4.0 release, there are no breaking changes, but there are some notable changes.

Printing

Fixed broken print utilities. Previously, using a .d-print-* class would unexpectedly overrule any other .d-* class. Now, they match our other display utilities and only apply to that media (@media print).

Fixed print preview rendering across browsers with new print styles that specify @pagesize.

Beta 3 changes

While Beta 2 saw the bulk of our breaking changes during the beta phase, but we still have a few that needed to be addressed in the Beta 3 release. These changes apply if you’re updating to Beta 3 from Beta 2 or any older version of Bootstrap.

Miscellaneous

Removed the unused $thumbnail-transition variable. We weren’t transitioning anything, so it was just extra code.

The npm package no longer includes any files other than our source and dist files; if you relied on them and were running our scripts via the node_modules folder, you should adapt your workflow.

Forms

Rewrote both custom and default checkboxes and radios. Now, both have matching HTML structure (outer <div> with sibling <input> and <label>) and the same layout styles (stacked default, inline with modifier class). This allows us to style the label based on the input’s state, simplifying support for the disabled attribute (previously requiring a parent class) and better supporting our form validation.

As part of this, we’ve changed the CSS for managing multiple background-images on custom form checkboxes and radios. Previously, the now removed .custom-control-indicator element had the background color, gradient, and SVG icon. Customizing the background gradient meant replacing all of those every time you needed to change just one. Now, we have .custom-control-label::before for the fill and gradient and .custom-control-label::after handles the icon.

To make a custom check inline, add .custom-control-inline.

Updated selector for input-based button groups. Instead of [data-toggle="buttons"] { } for style and behavior, we use the data attribute just for JS behaviors and rely on a new .btn-group-toggle class for styling.

Removed .col-form-legend in favor of a slightly improved .col-form-label. This way .col-form-label-sm and .col-form-label-lg can be used on <legend> elements with ease.

Custom file inputs received a change to their $custom-file-text Sass variable. It’s no longer a nested Sass map and now only powers one string—the Browse button as that is now the only pseudo-element generated from our Sass. The Choose file text now comes from the .custom-file-label.

Input groups

Input group addons are now specific to their placement relative to an input. We’ve dropped .input-group-addon and .input-group-btn for two new classes, .input-group-prepend and .input-group-append. You must explicitly use an append or a prepend now, simplifying much of our CSS. Within an append or prepend, place your buttons as they would exist anywhere else, but wrap text in .input-group-text.

Validation styles are now supported, as are multiple inputs (though you can only validate one input per group).

Sizing classes must be on the parent .input-group and not the individual form elements.

Beta 2 changes

While in beta, we aim to have no breaking changes. However, things don’t always go as planned. Below are the breaking changes to bear in mind when moving from Beta 1 to Beta 2.

Breaking

Removed $badge-color variable and its usage on .badge. We use a color contrast function to pick a color based on the background-color, so the variable is unnecessary.

Responsive tables now generate classes for each grid breakpoint. This breaks from Beta 1 in that the .table-responsive you’ve been using is more like .table-responsive-md. You may now use .table-responsive or .table-responsive-{sm,md,lg,xl} as needed.

Dropped Bower support as the package manager has been deprecated for alternatives (e.g., Yarn or npm). See bower/bower#2298 for details.

Bootstrap still requires jQuery 1.9.1 or higher, but you’re advised to use version 3.x since v3.x’s supported browsers are the ones Bootstrap supports plus v3.x has some security fixes.

Removed the unused .form-control-label class. If you did make use of this class, it was duplicate of the .col-form-label class that vertically centered a <label> with it’s associated input in horizontal form layouts.

Changed the color-yiq from a mixin that included the color property to a function that returns a value, allowing you to use it for any CSS property. For example, instead of color-yiq(#000), you’d write color: color-yiq(#000);.

Highlights

Introduced new pointer-events usage on modals. The outer .modal-dialog passes through events with pointer-events: none for custom click handling (making it possible to just listen on the .modal-backdrop for any clicks), and then counteracts it for the actual .modal-content with pointer-events: auto.

Summary

Here are the big ticket items you’ll want to be aware of when moving from v3 to v4.

Browser support

Dropped IE8, IE9, and iOS 6 support. v4 is now only IE10+ and iOS 7+. For sites needing either of those, use v3.

Added official support for Android v5.0 Lollipop’s Browser and WebView. Earlier versions of the Android Browser and WebView remain only unofficially supported.

Global changes

Flexbox is enabled by default. In general this means a move away from floats and more across our components.

Build system overhauled to use a series of npm scripts instead of Grunt. See package.json for all scripts, or our project readme for local development needs.

Non-responsive usage of Bootstrap is no longer supported.

Dropped the online Customizer in favor of more extensive setup documentation and customized builds.

Added dozens of new utility classes for common CSS property-value pairs and margin/padding spacing shortcuts.

Grid system

Moved to flexbox.

Added support for flexbox in the grid mixins and predefined classes.

As part of flexbox, included support for vertical and horizontal alignment classes.

Updated grid class names and a new grid tier.

Added a new sm grid tier below 768px for more granular control. We now have xs, sm, md, lg, and xl. This also means every tier has been bumped up one level (so .col-md-6 in v3 is now .col-lg-6 in v4).

xs grid classes have been modified to not require the infix to more accurately represent that they start applying styles at min-width: 0 and not a set pixel value. Instead of .col-xs-6, it’s now .col-6. All other grid tiers require the infix (e.g., sm).

Updated grid sizes, mixins, and variables.

Grid gutters now have a Sass map so you can specify specific gutter widths at each breakpoint.

Updated grid mixins to utilize a make-col-ready prep mixin and a make-col to set the flex and max-width for individual column sizing.

Changed grid system media query breakpoints and container widths to account for new grid tier and ensure columns are evenly divisible by 12 at their max width.

Grid breakpoints and container widths are now handled via Sass maps ($grid-breakpoints and $container-max-widths) instead of a handful of separate variables. These replace the @screen-* variables entirely and allow you to fully customize the grid tiers.

Media queries have also changed. Instead of repeating our media query declarations with the same value each time, we now have @include media-breakpoint-up/down/only. Now, instead of writing @media (min-width: @screen-sm-min) { ... }, you can write @include media-breakpoint-up(sm) { ... }.

Components

Dropped panels, thumbnails, and wells for a new all-encompassing component, cards.

Dropped the Glyphicons icon font. If you need icons, some options are:

See the Extend page for a list of alternatives. Have additional suggestions? Please open an issue or PR.

Dropped the Affix jQuery plugin.

We recommend using position: sticky instead. See the HTML5 Please entry for details and specific polyfill recommendations. One suggestion is to use an @supports rule for implementing it (e.g., @supports (position: sticky) { ... })/

If you were using Affix to apply additional, non-position styles, the polyfills might not support your use case. One option for such uses is the third-party ScrollPos-Styler library.

Dropped the pager component as it was essentially slightly customized buttons.

Refactored nearly all components to use more un-nested class selectors instead of over-specific children selectors.

By component

This list highlights key changes by component between v3.x.x and v4.0.0.

Reboot

New to Bootstrap 4 is the Reboot, a new stylesheet that builds on Normalize with our own somewhat opinionated reset styles. Selectors appearing in this file only use elements—there are no classes here. This isolates our reset styles from our component styles for a more modular approach. Some of the most important resets this includes are the box-sizing: border-box change, moving from em to rem units on many elements, link styles, and many form element resets.

Typography

Moved all .text- utilities to the _utilities.scss file.

Dropped .page-header as, aside from the border, all its styles can be applied via utilities.

.dl-horizontal has been dropped. Instead, use .row on <dl> and use grid column classes (or mixins) on its <dt> and <dd> children.

Custom <blockquote> styling has moved to classes—.blockquote and the .blockquote-reverse modifier.

.list-inline now requires that its children list items have the new .list-inline-item class applied to them.

Images

Renamed .img-responsive to .img-fluid.

Renamed .img-rounded to .rounded

Renamed .img-circle to .rounded-circle

Tables

Nearly all instances of the > selector have been removed, meaning nested tables will now automatically inherit styles from their parents. This greatly simplifies our selectors and potential customizations.

Responsive tables no longer require a wrapping element. Instead, just put the .table-responsive right on the <table>.

Buttons

Renamed .btn-default to .btn-secondary.

Dropped the .btn-xs class entirely as .btn-sm is proportionally much smaller than v3’s.

The stateful button feature of the button.js jQuery plugin has been dropped. This includes the $().button(string) and $().button('reset') methods. We advise using a tiny bit of custom JavaScript instead, which will have the benefit of behaving exactly the way you want it to.

Note that the other features of the plugin (button checkboxes, button radios, single-toggle buttons) have been retained in v4.

Dropped push and pull modifier classes for the new flexbox-powered order classes. For example, instead of .col-8.push-4 and .col-4.pull-8, you’d use .col-8.order-2 and .col-4.order-1.

Added flexbox utility classes for grid system and components.

List groups

Rewrote component with flexbox.

Replaced a.list-group-item with an explicit class, .list-group-item-action, for styling link and button versions of list group items.

Added .list-group-flush class for use with cards.

Modal

Rewrote component with flexbox.

Given move to flexbox, alignment of dismiss icons in the header is likely broken as we’re no longer using floats. Floated content comes first, but with flexbox that’s no longer the case. Update your dismiss icons to come after modal titles to fix.

The remote option (which could be used to automatically load and inject external content into a modal) and the corresponding loaded.bs.modal event were removed. We recommend instead using client-side templating or a data binding framework, or calling jQuery.load yourself.

Navs

Instead of HTML-specific selectors like .nav > li > a, we use separate classes for .navs, .nav-items, and .nav-links. This makes your HTML more flexible while bringing along increased extensibility.

Navbar

The navbar has been entirely rewritten in flexbox with improved support for alignment, responsiveness, and customization.

Responsive navbar behaviors are now applied to the .navbar class via the required.navbar-expand-{breakpoint} where you choose where to collapse the navbar. Previously this was a Less variable modification and required recompiling.

.navbar-default is now .navbar-light, though .navbar-dark remains the same. One of these is required on each navbar. However, these classes no longer set background-colors; instead they essentially only affect color.

Navbars now require a background declaration of some kind. Choose from our background utilities (.bg-*) or set your own with the light/inverse classes above for mad customization.

Given flexbox styles, navbars can now use flexbox utilities for easy alignment options.

.navbar-toggle is now .navbar-toggler and has different styles and inner markup (no more three <span>s).

Dropped the .navbar-form class entirely. It’s no longer necessary; instead, just use .form-inline and apply margin utilities as necessary.

Navbars no longer include margin-bottom or border-radius by default. Use utilities as necessary.

All examples featuring navbars have been updated to include new markup.

Pagination

Rewrote component with flexbox.

Explicit classes (.page-item, .page-link) are now required on the descendants of .paginations

Dropped the .pager component entirely as it was little more than customized outline buttons.

Breadcrumbs

An explicit class, .breadcrumb-item, is now required on the descendants of .breadcrumbs

Labels and badges

Renamed .label to .badge to disambiguate from the <label> element.

Dropped the .badge component as it was nearly identical to labels. Use the .badge-pill modifier together with the label component instead for that rounded look.

Badges are no longer floated automatically in list groups and other components. Utility classes are now required for that.

.badge-default has been dropped and .badge-secondary added to match component modifier classes used elsewhere.

Panels, thumbnails, and wells

Dropped entirely for the new card component.

Panels

.panel to .card, now built with flexbox.

.panel-default removed and no replacement.

.panel-group removed and no replacement. .card-group is not a replacement, it is different.

.panel-heading to .card-header

.panel-title to .card-title. Depending on the desired look, you may also want to use heading elements or classes (e.g. <h3>, .h3) or bold elements or classes (e.g. <strong>, <b>, .font-weight-bold). Note that .card-title, while similarly named, produces a different look than .panel-title.

The .hidden and .show classes have been removed because they conflicted with jQuery’s $(...).hide() and $(...).show() methods. Instead, try toggling the [hidden] attribute or use inline styles like style="display: none;" and style="display: block;".

All .hidden- classes have been removed, save for the print utilities which have been renamed.

Rather than using explicit .visible-* classes, you make an element visible by simply not hiding it at that screen size. You can combine one .d-*-none class with one .d-*-block class to show an element only on a given interval of screen sizes (e.g. .d-none.d-md-block.d-xl-none shows the element only on medium and large devices).

Note that the changes to the grid breakpoints in v4 means that you’ll need to go one breakpoint larger to achieve the same results. The new responsive utility classes don’t attempt to accommodate less common cases where an element’s visibility can’t be expressed as a single contiguous range of viewport sizes; you will instead need to use custom CSS in such cases.